Organopolylithium polymerization initiators and their preparation



United States Patent 3,296 150 ORGAN OPOLYLITHIUM lOLYMERIZATION INI-TIATORS AND THEIR PREPARATION Gerald R. Kahle, Bartlesville, 0kla.,assignor to Phillips Petroleum Company, a corporation of Delaware NoDrawing. Fiied Aug. 27, 1962, Ser. No. 219,787 4 Claims. (Cl. 252-.431)

This invention relates to the preparation of polymers of conjugateddienes. In accordance with one aspect, this invention relates to animproved method for preparing organopolylithium polymerizationinitiators. In another aspect, this invention relates to the initiatorcompositions thus prepared and to the use of these initiators in thepolymerization of conjugated dienes.

In recent years, there has been a great deal of activity in thedevelopment of processes for producing olefin polymers. Polymers ofmonoolefins such as ethylene and propylene, prepared by these processeshave received wide acceptance by many industries. The more recentdiscovery in the field of diene polymerization of certain so-calledstereospecific catalysts, which make possible the formation of polymershaving a desired configuration, has aroused considerable interest. Thepolymers formed by the use of these catalysts often have outstandingphysical properties which render them equal to or even superior tonatural rubber.

Among the various new polymers developed in the solution polymerizationof conjugated dienes using organometal initiator systems are the highcispolymers of isoprene prepared in the presence of organopolylithiuminitiators. Reaction products of lithium with polyarylsubstitutedethylenes are effective initiators for the polymerization of conjugateddienes, either alone or in admixture with each other, or in admixturewith other types of polymerizable monomers. Heretofore, these reactionproducts, or addu-cts, have generally been prepared in polar solventssuch as ethers and the method is satisfactory so far as adduct formationis concerned. A polar solvent is, however, undesirable in polymerizationsystems where the production of certain types of polymers, e.g., highcis-polyisoprene and low vinyl polybutadiene, is desired. A polarsolvent causes a decrease in the cis content of polyisoprene and anincrease in the vinyl content of polybutadiene.

One method which has been proposed for circumventing the difficultiesaccompanying the use of a polar solvent involves the replacement of asubstantial portion of it with a hydrocarbon diluent such as a parafiin,cyclopar-aflin, or aromatic hydrocarbon, e.g. benzene, toluene, or thelike. By suitable adjustment of operating procedures, the quantity ofthe polar solvent can be drastically reduced and its effect onsubsequent polymerizations minimized. One disadvantage in this type ofprocess is that two steps are necessary for the preparation of theinitiator. In addition, replacement of one medium with another willobviously increase operating costs.

The present invention is primarily concerned with an improved processfor the preparation of organopolylithium initiators and to theirsubsequent use for the polymerization of conjugated dienes wherein thedisadvantages of the prior art preparation processes are obviated.

Accordingly, an object of this invention is to provide novel conjugateddiene polymerization initiator compositions.

Another object of this invention is to provide a method 3,296,150Patented Jan. 3, 1967 jugated dienes in the presence oforganopolylithium initiators.

Other and further objects and advantages of the invention will becomeapparent to those skilled in the art upon consideration of theaccompanying disclosure and the appended claims.

According to the invention, it has now been found that reaction productsof lithium with polyaryl-substituted ethylenes can be prepared in asingle step in the presence of an acetylenic compound as the reactionmedium. It has been further found that these reaction products are veryeffective initiators for the polymerization of conjugated dienes. It hasbeen found that polyisoprene prepared with the initiators preparedaccording to the invention has a much higher cis content than thatobtained from initiator systems containing polar solvents such asethers. It has also been found that butadiene polymers obtainedemploying the initiators prepared according to the invention have a muchlower vinyl content than when prepared in systems containing others orother polar solvents.

Acetylenic compounds employed as media for the reaction of lithium withpolyaryl-substituted ethylenes according to the invention are liquidunder the reaction conditions and the triple bond is in an internalposition. Acetylenic compounds that can be employed according to theinvention have the structural formula:

wherein R is a hydrocarbon radial selected from alkyl, aryl andcycloalkyl radicals and combinations of these. The acetylenic compoundsemployed generally contain from 4 to 20, inclusive, carbon atoms.Acetylenic compounds preferred are those containing from 4 to 10 totalcarbon atoms per molecule.

Representative examples of acetylenic compounds that can be employedinclude 2-butyne (dimethylacetylene), Z-pentyne, 4-methyl-2-pentyne,2-hexyne, 3-hexyne, 2- heptyne, 3-heptyne, 4-methyl-3-heptyne, 2-octyne,3- octyne, 4-nonyne, Z-decyne, S-decyne, dodecyne, 6-dadecyne,3-butyl-5-octyne, 8-tetradecyne, 2-hexadecyne, 3-octadecyne,6,6-diethyl-2-hexadecyne, 2-eicosyne, diphenylacetylene, 1 phenyl 1propyne (methylphenylacetylene), l-phenyl-l-butyne(ethylphenylacetylene), dibenzylacetylene, dicyclohexylacetylene,dicyclopentylacetylene, l-cyclohexyl-l-butyne (ethycyclohexylacetylene),cyclohexylphenylacetylene, cyclohexylcyclopentylacetylene, and the like.

According to the invention, lithium is contacted under reactionconditions with at least one polyaryl-substituted ethylene in at leastone of the above-defined acetylenic compounds as the reaction medium.The polyaryl-substituted ethylenes that can be employed include thosecompounds which contain 2, 3 or 4 aryl groups such as phenyl and/ ornaphthyl, for example, 1,1-diphenylethylene, 1,2-diphenylethylene(stilbene), triphenylethylene, tetraphenylethylene,l-phenyl-l-naphthylethylene, 1,2- dinaphthylethylene,1,1-diphenyl-2-naphthylethylene, trinaphthylethylene and the like.

The lithium employed for preparing the initiators of the invention canbe used in any form desired such as wire, chunks, or shot, or in afinely divided state. When preparing the initiators, the lithium andpolyaryl-substituted ethylene are contacted in an acetylenic hydrocarbonreaction medium under mild agitation conditions, or vigorous agitationif desired, in an inert atmosphere such as argon, helium, krypton,xenon, neon, methane, ethane, and the like. The time required forformation of the reaction product depends upon various factors such astemperature, rate of agitation, ratio of reactants, and the like. Ingeneral, the time required is in the range of from about minutes to 100hours or longer. The temperature employed for reacting lithium with thepolyaryl-substituted ethylene generally ranges from about to 100 C. Theacetylenic hydrocarbons employed as the reaction media for preparing theinitiators of this invention do not polymerize under the conditionsemployed either for preparing the initiators or for subsequentpolymerization.

The monomers which can be polymerized in the presence of the lithiuminitiators of our invention are conjugated dienes containing from 4 to12 carbon atoms, preferably 4 to 8 carbon atoms per molecule. Examplesof suitable conjugated dienes that can be used include 1,3-butadiene,2-methyl-1,3-butadiene (isoprene), 2,3- dirnethyl-1,3-butadiene,1,3-pentadiene, 2-methyl-L3- pentadiene, 2,3-dimethyl-1,3-pentadiene,3-methyl-1,3- pentadiene, 2-phenylbutadiene, 3-butyl-1,3-octadiene, 3,4-dimethyl-1,3-hexadiene, and the like. Conjugated dienes containinghalogen and alkoxy substituents along the chain can also be employed,such as chloroprene, fluoroprene, 2-rnethoxy-1,3-butadiene,2-ethoxy-3-ethyl-1,3- butadiene, and 2-ethoxy-3-methyl-1,3-hexadiene.Conjugated dienes can be polymerized alone or in admixture with eachother to form copolymers, or block copolymers. Block copolymers can beprepared from two or more con- 'jugated dienes by charging one compoundinitially, allowing it to polymerize, and then adding a secondconjugated diene and allowing it to polymerize.

As hereinbefore mentioned, the initiators described herein are ofparticular interest for the production of high cis polyisoprene andbutadiene homopolymers and copolymers in which the conjugated dieneportion has a low vinyl content. The polyisoprene product obtainedaccording to the invention has a raw cis content above 60 percent andgenerally above 70 percent.

In addition to homopolymers and copolymers of conjugated dienes,copolymers of conjugated dienes with other monomers containing a CH Cgroup, such as vinyl-substituted aromatic compounds, can be made by theprocess of this invention. The..vinyl-substituted aromatic compoundsinclude styrene, l-vinylnaphthalene, 2- vinylnaphthalene, and alkyl,cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy, and dialkylaminoderivatives thereof in which the total number of carbon atoms in thecombined substituents is generally not greater than 12. Examples ofthese aromatic monomers include 3-methylstyreue (3-vinyltoluene),3,5-diethylstyrene,

4-n-propylstyrene, 2,4,6-trimethylstyrene, 4-dodecylstyrene,3-methyl-5-n-hexylstyrene, 4-cyclohexylstyrene,

4-phenylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene,

3,5 -diphenylstyrene, 2,4,6-tri-tert-butylstyrene,2,3,4,5-tetramethylstyrene,

4- (4-phenyl-n-butyl) styrene,3-(4-n-hexylphenyl)styrene-4-methoxystyrene, 3,5 -diphenoxystyrene,3-decoxystyrene, 2,6-dimethyl-4-hexoxystyrene, 4-dimethylaminostyrene,3,5-diethylaminostyrene, 4-methoxy-6-di-n-propylaminostyrene,4,5-dimethyl-l-vinylnaphthalene, 3-ethyl-1-vinylnaphthalene,6-isopropyl-l-vinylnaphthalene, 2,4-diisopropyl-l-vinylnaphthalene,3,6-di-p-tolyl-l-vinylnaphthalene, 6-cyclohexyl-l-vinylnaphthalene,4,5-diethyl-8-octyl-l-vinylnaphthalene,3,4,5,6-tetramethyl-l-vinylnaphthalene,

and the like. Block or random copolymers of conjugated dienes andvinyl-substituted aromatic compounds can be formed. The presence of asmall amount of polar compound encourages random copolymerizationbetween con-.

jugated dienes and vinyl-substituted aromatic compounds.

Block copolymers can also be prepared from conjugated dienes and polarmonomers which are introduced.

after the conjugated diene has polymerized. These polar monomers includevinylpyridines and vinylquinolines.

such as 2-vinylpyridine, 4-vinylpyridine,

3 ,5 -diethyl-4-vinylpyridine, S-methyl-Z-vinylpyridine,S-n-octyLZ-vinylpyridine,

3-n-dodecyl-Z-vinylpyridine,

3,5 -di-n-hexyl-4-vinylpyridine, 5-cyclohexyl-2-vinylpyridine,4-phenyl-2-vinylpyridine,

3,5 -di-tert-butyl-2-vinylpyridine, 3-benzyl-4-vinylpyridine,6-methoxy-2-vinylpyridine, 4-phenoxy-2-vinylpyridine,4-dimethylamino-2-vinylpyridine,3,5-dimethyl-4-diamylamino-Z-vinylpyridine, 2-vinylquinoline,4-vinylquinoline, 2-tert-butyl-4-vinylquinoline,3-methyl-4-vinylquinoline, 3-cyclohexyl-4-vinylquinoline,

5 3-methyl-4-ethoxy-2-vinylquinoline,

. jugated diene polymers.

l-vinylisoquinoline,

3-vinylisoquinolirie, 4-tert-dodecyl-l-vinylisoquinoline,3-dimethylamino-3-vinylisoquinoline, 4-benzyl-3-vinylisoquinoline,4-phenyl-l-vinylisoquinoline, and the like.

When it is desired that the polymer formed exhibitrubberycharacteristics the conjugated diene should be em? ployed as amajor amount of the monomer polymerized. Ihe initlator compositionsprepared according to this invention are particularly valuable informing these con- It should be understood, however, that theseinitiator vinyl-substituted aromatic compounds or the polar monomersnamed. Also, block copolymers can be formed between thevinyl-substituted aromatic compounds and compositions can also beusedwhenpreparmg homopolymers or copolymers of the i itiator employed willrange from about 0.1 to 100 millimoles per hundred grams of monomer withthe preferred range being from about 0.25 to 30 millimoles per hundredgrams of monomer.

The polymerization reaction is generally carried out at a temperatureranging from about -100 to about 150 C., preferably from about 75 toabout +75 C. The particular temperature employed will depend on both themonomers and the initiator used in preparing the polymers. It ispreferred that the polymerization be carried out in the presence of asuitable diluent, such as benzene, toluene, cyclohexane,methylcyclohexane, xylene, n-butane, n-hexane, n-heptane, isooctane, orthe like. Generally, the diluent is selected from hydrocarbons, forexample paraffins, cycloparafiins, or aromatics containing from 4 tocarbon atoms per molecule.

Numerous variations in operative procedure can be employed. The processof the invention can be carried out as a batch process by chargingmonomer or monomers into a reactor containing initiator and diluent.

If desired, the organopolylithium initiator dispersed in an acetylenichydrocarbon (reaction medium) can be first charged to a suitablereactor, which can contain diluent, and then charge the monomer to thereactor. The hydrocarbon diluent used for polymerization can be chargedalong with the initiator or monomer or both. In all cases thepolymerization is preferably carried out in an inert atmosphere such asan atmosphere of nitrogen, helium, argon, or the like.

The polymers that are prepared according to the inventi-on can rangefrom liquids to solid rubbery materials. The unquenched polymersolutions can be treated with various reagents to introduce functionalgroups replacing the terminal lithium atoms on the polymer moleculeresulting from the polymerization itself. For example, polymer insolution can be contacted with carbon dioxide to replace the lithiumatoms with COOH groups. Other functional groups which can be introducedinclude fiSI-I, -OH, halogen and the like.

As indicated above, the polymer products can range from liquids torubbery materials and the liquid polymers can subsequently be cured toform solids. The polymers can be. compounded 'by the various methodssuch as have been used in the past for compounding natural and syntheticrubbers using, for example, a roll mill or a Banbury mixer. Reinforcingagents such as carbon black and mineral fillers, plasticizers,vulcanizing agents, vulcanization accelerators, antioxidants, and

the like such as have been employed in natural and synthetic rubbers canbe used when compounding the rubbery polymers of the invention. Thepolymers of the invention can be blended with other polymers such asnatural rubber, other synthetic rubbers, polyolefins such aspolyethylene, and the like.

The polymeric products of the invention are useful as adhesives, pottingcompounds, sealants, tread stocks, and for making many types of moldedobjects.

A more comprehensive understanding of the invention can be obtained byreferring to the following illustrative examples which are not intended,however, to be unduly limitative of the invention.

Example I A polymerization initiator was prepared by the reaction oflithium with trans-stilbene (1,2-diphenylethylene) in 3-hexyne as thereaction medium. The reaction was effected in an atmosphere of argon.The following recipe was employed:

6 The reaction product, 1,2-dilithio-1,2-diphenylethane or lithiumstilbene adduct, was employed as the initiator for the production ofcis-polyisoprene in accordance with the following recipe:

Isoprene, parts by weight .100 n-Pentane, parts by weight 1000Initiator, millimoles 10 Temperature, F. 122 Time, hours 48 Conversion,percent 50 Pentane was charged first, the reactor was purged withnitrogen, isoprene was added, and then the initiator. At the conclusionof the polymerization, the reaction was shortstopped with isopropylalcohol to which was added the antioxidant,2,2-methylene-bis(4-methyl-6-tert-butylphenol) dissolved in isopropylalcohol. One part by weight per 100 parts polymer of the antioxidant wasused. The product was coagulated with isopropyl alcohol, separated, anddried. It had the following properties:

1 One-tenth gram of polymer was placed in a wire cage made from meshscreen and the cage was placed in ml. of

toluene contained in a wide-mouth, .t-ounce bottle. After standing atroom temperature (approximately 77 F.) for 24 hours, the cage wasremoved and the solution was filtered through a. sulfur absorption tubeof grade 0 porosity to remove any solid particles present. The resultingsolution was run through a. Medalia-type viscometer supported in a 77 F.bath. The viscometer was previously calibrated with toluene. Therelative viscosity is the ratio of the viscosity of the polymer solutionto that of toluene. The inherent viscosity is calculated by dividing thenatural logarithm of the relative vlscosity by the weight of theoriginal sample.

Determination of gel was made along with the inherent viscositydetermination. The wire cage was calibrated for toluene retention inorder to correct the weight of swelled gel and to determine accuratelythe weight of dry gel. The empty cage was immersed in toluene and thenallowed to drain three minutes in a closed widemouth, two-ounce bottle.A piece of folded quarter-inch hardware cloth in the bottom of thebottle supported the cage with minimum contact. The bottle containingthe cage was weighed to the nearest 0.02 gram during a. minimumthree-minute draining period after which the cage was withdrawn and thebottle again weighed t0 the nearest 0.02 gram. The difference in the twoweighings is the weight of the cage plus the toluene retained by it, andby subtracting the weight of the empty cage from this value, the weightof toluene retention is found, i.e., the cage calibration. In the geldetermination, after the cage containing the sample had stood for 24hours in toluene, the cage was withdrawn from the bottle with the aid offorceps and placed in the two-ounce bottle. The same procedure wasfollowed for determining the weight of swelled gel as was used forcalibratiou of the cage. The weight of swelled gel was corrected bysubtracting the cage calibration.

These data show that high-cis polyisoprene can be obtamed using aninitiator prepared in an acetylenic medium. Example II Thelithium-stilbene adduct described in Example I was employed as theinitiator for the polymerization of buta- The procedure for preparationand recovery of the polymer was the same as in Example I. The producthad the following properties:

Inherent viscosity 3.9 Gel, percent 0 Microstructure, percent:

cis, by difference 44.8 trans 47.8 Vinyl 7.4

See footnotes 1 and 2 above.

7 Example III A polymerization initiator was prepared by the reaction oflithium with trans-stilbene (1,2-diphenylethylene) in' cyclohexane asthe reaction medium. The reaction was elfectedin an atmosphere of argon.The following recipe was employed:

Moles Trans-stilbene 1.0 Lithium wire 3.0 Cyclohexane 5.0 Temperature,F., argon atmosphere 122 The molarity was determined by withdrawing asample of the reaction mixture and titrating it with 0.1 N HCl.

The reaction mixture obtained had the following molarity after variousreaction periods:

Theor. molarity 1.39 Molarity after:

days 0.01 8 days 0.03 14 days 0.06 36 days 0.09

The reaction product obtained above was employed as the initiator forthe polymerization of isoprene in accordance with the following recipe:

Isoprene 100 n-Pentene 1000 Initiator, millimoles 5 and Charge order:n-Pentane, nitrogen purge, isoprene,

initiator, 20 hours polymerization period.

11.25 micron band. In the presence of a high cis-polyisoprene, trans isnot detectable since trans is measured at the 8.75 micron band. The rawcis andraw 3,4-addition are converted to normalized values (assuming.

cis+ 3,4-addition= 100) as follows:

raw cis percent raw cis percent+ raw 3,4-addition, percent =normalizedcis percent The cis was raw 3,4-addition percent raw cis pereent+raw3,4-addition, percent =normalized 3,4-addition percent It will beevident to those skilled in the art that many variations andmodifications can be practiced upon consideration of the foregoingdisclosure. Such variations and modifications are believed to be withinthe spirit and scope of the present invention.

I claim:

'1. A process for forming an organopolylithium polym erization initiatorcomposition which comprises contacting. lithium with apolyaryl-substituted ethylene compound containing from 2.to 4 arylgroups selected from the group consisting of phenyl and naphthyl in aninert nonpolymerizable reaction medium comprising an acetylenichydrocarbon material having from 4 to 20, inclusive, total carbon atomshaving the structural formula:

RCECR wherein R is a hydrocarbon radical selected from alkyl,

'aryl, and cycloalkyl radicals and combinations of these at atemperature in the range -20 to 100 C.

2. A process according to claim 1 wherein at least 2 moles of lithiumare contacted with each mole of said ethylene compound.

3. A process according to claim 1 wherein said compound is1,2-diphenylethylene (trans-stilbene).

4. A process for forming an organopolylithium polyrnerization initiatorcomposition which comprises contacting. (a) lithium with (b)1,2-diphenylethylene in (c) 3-hexyne at a temperature in the range 20 to100 C.

References Cited by the Examiner UNITED STATES PATENTS 2,898,327 8/1959McCulloch et a1 252-431 3,048,568 8/1962 Cleary 260-94.2 3,159,58712/1964 Uraneck et al 260-942 3,170,903 2/ 1965 Stearns 26094.2

FOREIGN PATENTS 817,695 8/ 1959 Great Britain.

JOSEPH L. SCHOFER, Primary Examiner.

LEON J. BERCOVITZ, Examiner.

C. R. REAP, I. CANTOR, Assistant Examiners.

1. A PROCESS FOR FORMIN AN ORGANOPOLYLITHIUM POLYMERIZATION INITIATORCOMPOSITION WHICH COMPRISES CONTACTING LITHIUM WITH APOLYARYL-SUBSTITUTED ETHYLENE COMPOUND CONTAINING FROM 2 TO 4 ARYLGROUPS SELECTED FROM THE GROUP CONSISTING OF PHENYL AND NAPHTYL IN ANINERT NONPOLYMERIZABLE REACTION MEDIUM COMPRISING AN ACETYLENICHYDROCARBON MATERIAL HAVING FROM 4 TO 20, INCLUSIVE, TO TOTAL CARBONATOMS HAVING THE STRUCTURAL FORMULA: